1. Technical Field
The present invention relates to novel compounds which inhibit BTK and their use as medicaments.
2. Background Information
Members of the protein kinase family of human enzymes play important regulatory roles in a multitude of distinct signal transduction processes due to their post-translational modification of specific proteins via the addition of a phosphate group (Hunter, Cell, 1987 50, 823-829). Bruton's tyrosine kinase (BTK) is a member of the Tec family of tyrosine kinases and plays a critical role in B cell development, activation and antibody production.
The contribution of BTK to B cell biology is exemplified in the X-linked agammaglobulinemia (XLA) immunodeficiency in humans (reviewed in Lindvall, Immunol Rev 2005, 203, 200-215 that display attenuated calcium signaling upon BCR engagement, lack mature B cells in periphery due to block between pro- and pre-B cells stage and have lower levels of circulating antibodies than normal healthy subjects. The outcome of recent clinical trials with B cell depleting anti-CD20 molecules in diseases such as rheumatoid arthritis (RA) and multiple sclerosis (MS) support the hypothesis that B cells offer an important intervention node for controlling autoimmune disorders (Townsend et al. 2010). As such, attenuation of B cell activation and proliferation via inhibition of BTK may offer similar therapeutic benefit and is consistent with the demonstrated resistance of BTK-deficient mice to collagen induced arthritis (Jansson, 1993, Clin Exp Immunol 94, 459-465) and experimental autoimmune encephalitis (Svensson et al. 2002 and Mangla et al 2004). Similarly, the clinical efficacy observed with a neutralizing antibody to the B cell stimulating factor BlyS supports a role for B cells in the pathophysiology of systemic lupus erythematosus (SLE) (La Cava 2010). Given the necessity for BTK for the production of autoantibodies, including anti-DNA antibodies, in murine models of SLE (Steinberg et al., 1982; Golding et al., 1983; Scribner et al., 1987; Seldin et al., 1987; Satterthwaite et al., 1998; Takeshita et al., 1998; Whyburn et. al., 2003), BTK inhibitors may offer therapeutic benefit to SLE patients.
Within myeloid cells, BTK signal transduction is necessary for the stimulated release of inflammatory cytokines such as TNF from stimulated monocytes (Horwood, J Exp Med, 2003, 1603-1611) and for optimal actin cytoskeletal organization and lacunar bone resorption in isolated osteoclasts (Danks, 2011, J Bone and Mineral Research, 26, 182-192). Bone marrow derived mast cells lacking BTK exhibit impaired activation-induced degranulation and cytokine release (ref). Given the role of BTK in signal transduction processes across multiple cell types implicated in the pathogenesis of autoimmune and allergic disorders, inhibition of BTK activity may provide clinical benefit in diseases such as RA, MS, SLE, asthma and allergic disorders.